A typical AC load, such as an incandescent light, is powered by a standard 120 volt AC supply. In one common form of a dimmer circuit, the AC supply is "chopped" each half cycle so that power is actually applied to the load for only a portion of each half cycle. A triac is often used for switching of power to the load. A zero crossing of the AC supply is sensed to trigger a delay circuit. The delay circuit outputs a pulse a select time after the zero crossing according to the amount of dimming required. The pulse gates the triac. The triac turns itself off at the subsequent zero crossing.
When a stepped voltage is applied across an inductive load, the impedance is infinitely high and decreases as the magnetic field is established. With extremely small values of current through an inductor, until the magnetic field is established, the triac does not have enough current to latch on. This is a problem in typical light dimming circuits which use a short turn-on pulse. As a result, due to inductive current delaying the establishment of adequate latching current, the triac will not be turned on.
The present invention is directed to solving the problems discussed above in a novel and simple manner.